These tests were carried out by having two crows match sets of cards with one another. The results were particularly fascinating as the crows managed to preform RMTS without ever having been trained to do so. This is significant because apes, such as gorillas and chimpanzees, are capable of learning RMTS but only after much training.
The crows did require training for IMTS which, unlike RMTS, does not involve understanding the relationship between items. This seems to indicate that crows have a very high natural sense of intuition when it comes to understanding the relationship between items. Seeing an animal preform such a feat raises questions about the true intelligence of crows and wild animals in general.